Regenerative tracking system



H. HARRIS, JR

REGENERATIVE TRACKING SYSTEM March 30, 1965 5 Sintesis-Sinaai. 1

Filed March 29. 194e INVENTOR HERBERT HAR/als, Je. i i lrgf R xa March 30, 1965 v H. HARRIS, JR 3,176,292v

REGENERTIVE TRACKING SYSTEM v' THRGE T INVENTOR HEEB EET HA eels, .ne

March 30,' 1965 l H. HARRls, JR 3,176,292

REGENERATIVE TRACKING VSYSTEM Filed March 29, 1946 3 Sheets-Sheet 3 REGENHPAT/vs F y TRACK/NG MEc//A/v/SM :I

-INVENTOvR HERBERT HAEElsN/e c; A|TORNEY United States Patent O 3,176,292 REGENERA'HVE TRACKENG SYS'EEM Herbert Harris, Jr., Cedarhui'st, NX., assigner to Sperry Rand Qorporation, a corporation of Deiaware Filed Mar. 29, i946, Ser. No. 658,164 27 Claims. (Cl. 343-3) This invention relates generally to the art of gun tire control although it may be used for other purposes, and more particularly to means for and methods of continuously directing gun fire so as to eifect hits against rapidly moving targets, such as airplanes. Although primarily intended as an anti-aircraft director, the apparatus of the present invention will obviously function equally well to solve the more simple lire control problems, such as directing fire against surface craft, stationary targets, and so forth.

This application is a continuation-in-part of pending application Serial No. 500,349 for Gun Directing System, filed in the UnitedStates Patent Ofiice on or about August 28, 1943, now US. PatentNo. 2,660,371, issued November 24, 1953.

Prior gun directors, such as those described in US. Patent No. 2,065,303 entitled Apparatus for the Control of Gun Fire, issued December 22, 1936, in the names of E. W. Chafee etal., and in copending U.S. application, Serial No. 470,686, for Gun Directing System, tiled December 30, 1942, in the names of D. I. Campbell and W. G. Wing, now U.S. Patent No. 2,492,355, issued December 27, 1949, include predicting apparatus which is based upon the assumption that the target flies at a constant speed in a constant direction during the projectile time of flight. While this assumption is very often valid, for example, during the bombing run of a bomber aircraft, it is obviously desirable to be able to fire effectively at targets dying in a curved path. U.S. application Serial No. 500,349, above referred to, now US. Patent No. 2,660,371, discloses apparatus for continuously indicating the actual `course the target is flying. From this course indication it is possible to tell Whether the straight line flight assumption is or is not valid. Auxiliary predicting apparatus is provided therein, which may be rendered effective when the course indicator indicates that the target is flying in a curved path, and which then operates to introduce a correction to compensate for the targets deviation from straight line flight.

The present invention particularly relates to novel regenerative tracking apparatus Which may be used in conjunction With either the radio automatic or optical manual tracking systems provided. This regenerative tracking apparatus operates to automatically take over the task of tracking the target as soon as accurate tracking has once been established by eitherl of the other tracking systems. v The regenerative trackingV apparatus thereafter maintainscorrect tracking as long as the target does not change its course or speed. The task of the radio automatic or optical manual tracking systems is thus reduced to that of compensating for changes in target course or s eed.

pAssume, for example, that a target is being tracked with a radio automatic tracking system of the character hereindescribed and that the tracker momentarily or for a short interval of time loses contact with the target being tracked due, perhaps, to confusion caused by enerny jamming or When an obstacle becomes interposed between the tracker and the target. During such interval of time, the input from the radio tracking system becomes zero and control is lost. By incorporating a regenerative tracking apparatus of the character herein set forth, the trackeris controlled automatically to follow the same path that the target was travelling and substan-A ICC tially at the same rate measured immediately before the target Was lost. When the signals are again available from the radio tracking system because the radio sight has again made contact with the target, radio tracking Will be resumed. In the interval during which the regenerative tracking apparatus has taken over complete control, some error may creep in, but upon the resumption of radio tracking the tracker will quickly eliminate such error and again provide radio control and accurate target data based on the true relative position of the target.

Accordingly, it is the principal object of the present invention to provide a regenerative tracking system for gun directors and similarly controlled apparatus.

Another object resides in providing a device for positioning a movable member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, in which a rst means is provided for controlling the angular rate of change of position of said member, and a second means is provided for maintaining preestablished rates of change of position of said member during inoperative periods of the first rate control means.

Further objects reside in the provision of a device of the foregoing character in which the means for maintaining the pre-established rates is controlled in accordance with a measure of the range of the object; in which the means for maintaining pre-established rates is `controlled in accordance with measures of the rate of change in position of said member in rectilinear coordinate values; and in which means for maintaining the pre-established rates is controlled in accordance with measures of the rate of change of position of said member and the range of the object.

Still another object lies in providing an error conversion mechanism for converting errors in rectangular or rectilinear coordinates to corresponding errors in quadrant elevation, angle of train and slant range.

The invention in another of its aspects relates to novel features of the instrumentalities described herein for achieving the principal objects of the invention and to novel principles employed in those instrumentalities, whether or not these features and principles are used for the said principal objects or in the said eld.

A further object of the invention is to provide improved apparatus and instrumentalities embodying novel features and principles, adapted for use in realizing the above objects and also adapted for use in other fields.

A still further object resides in providing a control signal for a servo mechanism for automatically maintaining a pre-established rate of operation of said servo wherein the signal is derived at least in part from the output of the servo mechanism and is a function of the terms or measures set forth in the equations hereinafter presented and derived.

With the foregoing and other objects in view, my invention includes the novel elements and the novel combinations, constructions and arrangement of parts hereinafter described and illustrated in the accompanying drawings, in which:

FIG. l is a fragmentary schematic diagram of a preferred form of the present invention;

FIG. 2 schematically represents the construction of the rectilinear converter of FIG. 1;

FIG. 3 is a fragmentary, schematic view in detail of the smoothing, differentiating and predicting circuit of FIG. 1;

FIG. 4 is a schematic representation of the regenerative tracking mechanism of FlG. 1;

FG. 5 schematically illustrates an alternative arrangement for embodying the regenerative tracking mechanism in a system of the'character shown in HG. `1; and

FIGS. 6-9 are rectilinear coordinate diagrams illustrating one manner in which the control terms or equations hereinafter presented are developed.

Similar characters of reference are used in all or" the above gures to indicate corresponding parts. Arrows are employed to indicate the direction of flow oi intormation or control inliuences.

Throughout the director of the present invention data is represented and transmitted by mechanical displacements, and direct and alternating potentials. It will be understood, where not stated, that a mechanical displacement so employed is proportional in magnitude to the magnitude of the quantity represented thereby, and corresponds in direction to the algebraic sign or' the quantity represented. Similarly the magnitude oi the direct or alternating potential is proportional to the magnitude of the quantity represented thereby, and the polarity or phase of the potential corresponds to the sign of the quantity.

ln FIG. 1 there is shown a schematic diagram of the Whole gun directing system of the present invention, the ultimate purpose of which is to electrically transmiL angle of train (A.T.), quadrant elevation (QE.) and uze setting (F) data to the guns. For the sake or clarity in the description, and simplicity in the explanation, the apparatus of which the invention herein described forms a part may be considered to accomplish its purpose in the following three distinct and more or less independent steps:

(l) Range finding and tracking apparatus is employed to obtain continuous spherical coordinate data representative of the present position of the target, that is, present azimuth (A0), resent elevation (E0) and present slant range (D0), obtained as proportional angular displacements of present position shafts, ll, 2 and 3, respectively.

(2) This present position spherical coordinate data is converted to corresponding present position rectangular coordinate data (x0, y0 and zo). As shown in applicacation Serial No. 560,349, now US. Patent No. 2,660,371, this data is combined with the projectile time of flight (tp) in suitable prediction apparatus to obtain the rectangular coordinates (xp, yp, and zp) of the predicted, or future, position of the target, that is, the point in space at which the target will be located at a time (tp) later. This predicted position data is obtained as proportional angular displacements of future position shafts.

(3) This predicted position data is employed in suitable ballistic mechanism to obtain angle of train (Aff.) and quadrant elevation (QE.) data for positioning the guns, fuze (F) data for cutting the projectile and time of liight (tp) data for use in the prediction apparatus. The angle of train, quadrant elevation, tuze, and time of flight data are obtained as proportional angular displacements of shafts.

The first problem, namely that of angularly displacing shafts ll, @and 3, respectively, in proportion to present azimuth (A0), present elevation (E0), and present slant range (Dn), Will now be considered. ln tracking the target in order to obtain azimuth and elevation data ltwo modes of operation are provided: (l) radio automatic, and (2) optical manual. The desired one of these modes of operation may be selected by suitably positioning selector switches d and 5 which, it will be understood, are simultaneously operated as a unit. In both radio and optical modes of operation range data it is automatically supplied from the radio sighting apparatus.

When switches d, 5 are in their optical position, an operator or operators actuate handwheels 6, '7, respectively, until the line or" sight delined by the telescope 3 is directed toward the target. Two eyepieces may be provided on telescope d as shown, one for each operator, through which they can see the target and thus determine whether the telescope has been properly oriented.

Handwheel d actuates a shaft 9 which in turn drives a permanent magnet generator lill, and also drives the l rotating contact arm lll of a linearly wound potentiometer l2, the opposite terminals of which are connected to a suitable constant source of voltage, such as battery l, and the intermediate terminal of the potentiometer winding is connected to ground, as shown. Accordingly, there will be provided on lead lfl, which is electrically connected to contact arm il, a direct voltage proportional in magnitude and corresponding in polarity to the angular displacement of handwheel o from a datum position. This voltage signal is placed in series with the output voltage or" generator lil which last voltage, as is well known, will be proportional in magnitude, and will correspond in polarity, to the rate at which handwheel 6 is being displaced. Accordingly, the voltage appearing on lead l5 will be the algebraic sum of two component voltages, one proportional to the displacement of handwheel 6 and the other proportional to the rate of said displacement.

The voltage on lead l5 is transmitted through switch d and is then added to the voltage appearing on output lead lle of the regenerative tracking mechanism indicated encrally at il?. For the present it will be assumed that the regenerative traclring mechanism is not operating (switch being -in the oft position), and that therefore no additional voltage is from the regenerative tracking mechanism. Accordingly, the voltage on lead 19 is identical with that on lead l5.

The voltage on lead i? is introduced into the azimuth ervo which be of any suitable type of s rvo unit pied to produce an angular displacement of its out- Jut shaft at a rate proportional in magnitude and orresnonding in direction to the magnitude and polarity of its input signal. Gutput shaft 2i actuates the present azimuth shaft ll through gearing Z2.

Rotated by shaft l is a gear Z3 engaging the large azimuth gear 24- wliich, in the embodiment illustrated, is xediy mounted in the director support. Thus, the existence of a voltage signal on lead l@ will cause gear 23, shaft l, and all of the rest or the director apparatus to wall; around iixed gear 2li at a rate proportional to the voltage on lead Accordingly, since the azimuth operator nas control of the voltage on lead i9 through his handwhcel o, he has complete control over the azimuth poistion oi the director, and 'ne may therefore continuously maintain tclescope d directed at the target in azimuth. When this has been accomplished the angular displacement of shait l is proportional to the present target azimuth angle (A0). i'resent azimuth data is then introd ced into the rectilinear converter 25 as the displacement oi shaft l.

rl`he purpose of the ator is to provide what is commonly termed aided tracking in order to facilitate he operators task of maintaining telescope 8 directed toward the target. if generator il@ were not provided, it will be apparent that pure rate tracking would be obtained since the director and telescope S would then rotate at a rate proportional to the displacement oi handwheel 6. By providing the generator, however, this rate is increased or decreased by a component proportional to the rate of handit/heel displacement. The time integral of the increment will be proportional to the time integral of the rate of displacement oi the handwheel. rl`he displacement of the director due to this increment will therefore be proportional to the displacement of the hand- .'heel. Thus, it is seen that if the generator alone were employed without the potentiometer i2, pure displacement tracking would be obtained wherein the actual displacement of the director would be proportional to the actual displacement of the handwheel. By employing both the generator and the potentiometer aided tracking is obtained wherein the director is displaced simultaneously at a rate and by an amount proportional to the displacement of the handwheel.

rEhe apparatus provided for control in manually tracking the target in elevation is identical with that just degener scribed for the azimuth control. Corresponding portions of the tracking control apparatus for elevation and azimuth have been given identical reference numbers but are primed in the case of the elevation control equipment.

In the case of elevation control, however, the present elevation shaft 2, driven from the elevation servo 26, rotates the line of sight defined by telescope 8 in a vertical plane through gearing 27, shaft 28, gearing 29, shaft 30 and gearing 31. Shaft 28 is also connected to the radio scanner, indicated generally at 32, of the radio sighting system to simultaneously rotate the line of sight thereof in elevation about an axis b-b paralleling the axis a-a of the telescope mounting.

As in the case of the azimuth control, the operator has complete control, through his handwheel 7, of the voltage appearing on lead 19', and therefore has complete control of the position of shaft 2 and of the orientation in elevation ofthe line of sight defined by the telescope 8 and the radio sighting system. Present elevation (E) is also introduced into the rectilinear converter 25 as a proportional rotation of present elevation shaft 2.

' Although, mainly for illustration purposes, I have illustrated handwheels 6 and 7 as the manually operated control members for controlling the director or sight, radio or optical, in azimuth and elevation, it will be understood of course that a single manually operable control, usually termed handle bars may be employed. Such handle bars are movable in azimuth and also in elevation by the operator and the movements thereof in these directions respectively control the azimuth and elevation servos in substantially the same manner as do the handwheels 6 and 7.

For radio automatic tracking, which is initiated by placing switches 4, in their radio position, there is provided a radio sighting system which is preferably of the 'ultra high frequency pulse type described in copending U.S. application Serial No. 441,188 for Radio Gun Control System led April 30, 1942, in the names `of C. G. Holschuh et al., now U.S. Patent No.,2,6l7,982 issued November ll, 1952. As more completely described in that application, a radio transmitter 33 includes means for generating short periodic pulses of ultra high frequency radio energy. These pulses of radio energy are transmitted to the antenna 34 of the radio scanner 32 through a suitable transmission channel for high frequency energy, such as a wave guide 35.

The antenna is mounted within a parabolic reflector 36 and is adapted to transmit into space in a fan-shaped beam along its axis 37 the pulses of electromagnetic energy supplied to antenna 34. Radio scanner 32 includes a spin motor 38 adapted to rotate antenna 34 about a spin axis 39 and the scanner as a whole rotates in azimuth and in `elevation while the antenna may spin in any position of the scanner. As shown, the axis V37 of `the parabolic reflector is slightly offset from spin axis 39 so that, as a result of its rotation, a conical portion of space is irradiated with short pulses of electromagnetic energy. The rate of rotation of antenna 34 about spin axis 39 may be of the orderof 200 times less than the pulse repetitionrate, so that all portions of the conical angle of space are irradiated.

lAlso included within the radio scanner 32 and rotated by the previously mentioned spin motor isV a two-phase generator 40 which generates two 90 phase displaced voltages and transmits these voltages, as on leads 41, to the azimuth and elevation detector circuits 42 and 43 to provide a time reference of the rotation of antenna 34.

As more fully explained in the above-mentioned copending application, should a target lie within the conical portion of space irradiated by the transmitted Waves, a portion of the electromagnetic energy striking the target will be reected back to the reflector 36 and received in the form of pulses corresponding to the transmitted pulses but delayed in time by an amount proportional `to the distanceito the target. These reflected pulses of electromagnetic energy are schematically indicated as being transmitted to the radio receiver 44, as by Wave guide 45. Should the target be lying along the spin axis 39, which is the line of sight defined by the radio system, it will be apparent that all the reflected pulses will be of the same intensity. On the other hand, if the target should not lie along spin axis 39, the intensity of the reflected pulses will vary substantially sinusoidally as the antenna or wave pattern rotates, the maximum intensity occurring at the time that axis 37 most nearly coincides with the target orientation.

A TR box 46 may be associated with the wave guide 45 so as to prevent the high intensity pulses delivered'by the transmitter from passing directly to the receiver 44. The TR box functions to block such high intensity signals but passes the lower intensity waves or pulses which are reflected back from the target and therefore substantially only the reiiected pulses are supplied to the receiver 44.

The radio receiver 44 includes detecting means for demodulating the received energy to provide a sinusoidal signal voltage corresponding to the substantially sinusoidal variation in intensity of the rellected pulses. This signal voltage is supplied by means of leads 47 and 47 to each of the two phase sensitive amplifiers 42 and 43, one for azimuth and one for elevation. By comparing the phase and magnitude of the sinusoidal signal voltage with one of the time reference voltages in the azimuth phase sensitive detector, there is produced upon output lead 4S a direct voltage corresponding in magnitude and polarity to the azimuth component of the angular deviation between the target orientation and spin axis 39. Similarly, by comparing the phase and magnitude of the sinusoidal signal voltage with the other time reference voltage in the elevation phase sensitive detector 43, there is produced upon output lead 48 a direct voltage Vcorresponding in magnitude'and polarity to the elevation component of the angular deviation between the target orientation and spin axis 39. These voltages, appearing on leads 43 and 48', can thus be thought of as azimuth and elevation error voltages, respectively, and as providing an electrical indication of theV angular error between the line of sight defined by the radio sighting system (spin axis 39) and the target orientation.

As shown, in the radio positions of switches 4, 5, these error voltages are introduced into the azimuth and elevation servos 2li, 26, respectively, to thereby cause rotations of the present azimuth shaft 1 and the present elevation shaft 2,. Rotations of these shafts in turn cause the line of sight deiined by the radio system to be moved in azimuth and elevation in a direction such as to align itself with a target orientation and thereby reduce the error voltage signals appearing on leads 48, 48 toward zero. In this manner the line of sight 39 of the radio sighting system is continuously and automatically maintained coincident with the target orientation, and present azimuth and present elevation data are continuouslyintroduced into rectilinear converter 25 as proportional angular displacements of shafts 1 and 2.

It willbe understood that telescope 8 and radio scanner 32 are preferably mounted -on the director such that the lines of -sight defined by each are at all times substantially parallel and coincident for all practical purposes.

In accordance with a preferred construction, the signal voltage delivered from the azimuth detector 42 and supplied to the lead 48 is not supplied directly, in controlling relation, to the azimuth servo but is modified or varied in accordance with the secant of the angle of elevation of the target or the angle which the line of sight 39 of the scanner makes with the azimuth plane. It will be noted that the signal supplied from the azimuth detector is proportional to the error or angular disagreement between the` line of sight 39 and the direction to a target as measured in a slant plane and not in the azimuth plane as it should be for correctcontrol of the azimuth servo. Therefore, the sensitivity of the azimuth servo, that is its degree of stiffness as compared to sluggishness, when controlled by a signal such as that derived from a radio'scanner will vary as a function of the secant of the angle between the azimuth plane and the slant plane in which the error is measured. To correct or compensate, a secant wound potentiometer T139 is preferably connected in series with a resistor 131 across the output of the azimuth detector. A secant potentiometer is one which has its resistance so wound that the voltage derived therefrom varies as a secant function of the angle through which the wiper is turned. As shown, the wiper 182 is driven from the output of the elevation servo through gearing and shafting or any other suitable transmission represented by the dot-dash line 183. With this arrangement the voltage supplied on lead 154 is substantially proportional to the azimuth error voltage as measured in the azimuth plane, and under such conditions the sensitivity of the azimuth servo system with respect to actual error will not materially vary. A more detailed disclosure of this secant correction the azimuth error signal appears in U.S. application Serial No. 517,008, tiled on or about Ianuary 5, 1944 in the names of G. E. White and DS. Pensyl, now U.S. Patent No. 2,784,402 issued March 5, 195'7.

Slant range (D) data is automatically and continuously obtained by the radio sighting system in both the radio and optical positions of switches 4, 5. For this purpose a delay network 49 is provided which receives on lead from the radio transmitter 33, voltage pulses corresponding in time phase to that of the transmitted radio pulses. Delay network 49 operates to delay these voltage pulses by a time proportional to the angular displacement of slant range shaft 3, which is received on shaft 5l. The resulting delayed pulses are then transmitted to a time comparator 52 as on lead 53. Also received by the time comparator are voltage pulses corresponding in time phase to that of the reflected pulses, as on lead 54. The time comparator is adapted to make a time comparison between the phase of the reilected pulses received on lead 54 and the-delayed transmitted pulses received on lead 53. If these pulses should be absolutely in phase, then the transmitted pulses received on lead 50 must have been delayed by an amount exactly proportional to the range of the target. Accordingly, when this condition is met, the angular position of shaft 3 represents the true present slant range to the target. A more detailed disclosure of this automatic range measuring system appears in U.S. patent application Serial No. 432,290, filed February 25, 1942, in the name of W. M. Silhavy, now U.S. Patent No. 2,789,284 issued April 16, 1957.

lf the reflected pulses received on lead S4 by the time comparator should not be in phase with the delayed transmitted pulses received on lead 53, the time comparator is adapted to produce an -output lead 55 a direct voltage corresponding in magnitude and polarity to the diiference in phase existing between these two pulses. This output voltage on lead 5S, which may be considered as a range error signal, is supplied together with the output Voltage appearing on lead 56 vfrom the regenerative tracking mechanism ll7, and is then introduced into the slant range servo 58 as on lead 5'7, as in the case of elevation and azimuth control. It will be assumed for the time being that the regenerative tracking mechanism 17 contributes no additional voltage on lead 56, and that therefore the voltage received by the slant range servo on lead 57 is the same as that appearing on lead 55.

This voltage input to the slant range servo 58 causes the servo to rotate its output shaft 59 at a rate proportional to the input signal. Shaft 59 `actuates the present slant range shaft 3 through gearing 60 in such a direction as to cause shaft 5l to increase or decrease the amount of delay introduced in the delay network 49 as required in order tomake the delayed pulses appearing on lead 53 coincide in time phase with the retiected pulses appearing on lead 54. As previously pointed out, when this condition of coincidence in time phase with respect to the voltages appearing on leads 53 and 54 has been obtained, the angular displacement of shaft 3 is proportional to the slant range to the target. This slant range data, appearing on shaft 3, is then lalso introduced into the rectilinear converter 25.

The purpose and operation of the regenerative tracking mechanism 17 will now be considered. It can be trigonometrically shown that, if the target flies a constant course or in a constant direction at a constant speed, the linear target `rates will remain constant while the spherical coordinate rates will change but there is a definite relationship between its present position, as determined by the present position spherical coordinate values (A0, E0 and Dn) supplied by the tracking mechanism, and the rates of change of its spherical coordinates (A0, E0 and D0). This relationship is given by the following formulae:

*in eos AO-y/'O sin A0 zo cos Eil-@ sin E0 2) E- (3) O=0 cos Erri-eo sin E0 (4) 1.502220 Sill A04-yh() COS A() wherein 0&0, y0, and an represent the linear target speeds in the East-West (x) direction, North-South (y) direction, and the vertical (z) direction, respectively, Ro represents the present horizontal target range, and R0 represents the horizontal range target rate. The target course and speed are fully determined by the three component rates d'0, 170 and a0, which are calculated as will hereinafter appear.

The derivation of the above presented formulae will best be understood by referring to FlGS. 6-9. FIG. 6 shows the position of target T in rectilinear coordinates measured along the x, y and z axes. The projection of the point T onto the plane including the x and y axes is represented by the point A. The x and y rectilinear coordinates of the points T and A are therefore represented respectively by the lines AB and BO. The point O represents the center of the system or the location of the director or scanner, and the rectilinear coordinate value along the z coordinate is the line TA. These rectilinear coordinate values are represented respectively by the designations xu, y0, zo. The azimuth angle BOA is A0 and the elevation angle TOA is E0, while the slant range D0 is the line OT.

The tracker, as hereinbefore indicated, supplies the values of A0, E0 and D0 to the computer or rectilinear converter which, as hereinafter pointed out, calculates the rectilinear coordinates of the position of the target T which are x0, y0, zu. The differentiating, smoothing and predicting circuit, as hereinafter described, provides as outputs the smoothed rates of change of the rectilinear coordinates which are aio, to and e'o. The values d20, y'o and a0 are represented as vector quantities in FI G. 7 as are also D0 (rate of change of slant range) and R0 (rate of change of horizontal range). Since the antenna-positioning and range systems of the tracker `are driven by azimuth, elevation and slant range data measured in polar coordinates, it is necessary to convert the aio, y0 and a'o values to azimuth, elevation and slant range polar coordinate rates and this function is served by the regenerative tracking mechanism.

To obtain the Formulae 1 through 4, above noted, the vector values of rco, 1'10 are projected onto the plane including the x and y axes as shown in FIG. 8. The R0 value is of course the rate of change of azimuth range or rate of change of range in said plane which may be considered the azimuth plane. By resolving the e0, Q70 vec- 9 tors into components along the linePP which is perpendicular to R0, the tangential rate 0R0 can be obtained.

(s) p20-:a0 cos .40-170 cos (9o-A0) COS Ao-o Sin A() From an examination of FIG. 6 it Will be seen that (7) R0=D0 eos E0 lly dividing both sides of Equation 6 by D0 cos E0, We ave (8) d20 COS lio-2]() Slll A0 D0 cos E0 i0 cos Atv-y0 sin A0 which is Equation 1. v

To calculate the elevation rate in polar coordinates,

We may resolve the 0&0 and y0 values along the R0 line in FIG. 8 to supply the value of the horizontal range rate pendicular to the slant range vector D0. VThe value 0D0 may therefore be represented as follows:

12) By dividing bothsides of Equation `12, by D0,`0 will result and isl 0 a0 cos Eo-o sin E0 which is Equation 2.

The slant range rate 1.30 isi-obtained byy resolving the vectors a0 and R0 along the D0 vector V(see FIG. 9). Therefore I 13) DFR, cos E0+z'0 cos (9o-E05 which is Equation 3.

The foregoing derivations of the Formulae 1- 4 VWill show mathematically how the outputs of the azimuth elevation and range servos, which are measured in polar` coordinate values, are transformed to the desired rectilinear coordinate, values. The rectilinear rate values are 1derived and, finally, measures of the desired control terms are supplied in accordancewith the formulae above noted. In the following, the operation ofthe 'variousV elements of the presentinvention Will be set forth inV detail to show 'how the various terms.of the formulae are obtained and combined in the manner represented `mathematically therein;` i g l As will be further described in detail with respect to FIG. 3, the component targetmrates (d0, Q20, and e0) are computed in the differentiatingsmoothing and `predicting circuit indicated generally at 61"and are produced as proportional angular displacements of output shafts 62, 63, and 64, respectively. Shafts' 62, 6 3 and 64 actuate shafts 65, 66 and 67 through bevel gearing to introduce these component target rates into the regenerative tracking mechanism 17. 'I`he spherical coordinates A0, E0 and D0 of the present target position are also introduced into the regenerative tracking mechanism from shafts 1, 2, and 3 by Way of shafts 68, 69 and 70, respectively. Present the regenerative tracking mechanism as a proportional angular displacement of shafts 71 and 72.

Having received A0, E0, D0, R0, 4&0, 120 and e0 as input data, the regenerative tracking mechanism, as will be described in detail hereinafter, is adapted to solve Equations 1 to 4 and, when switch 18 is in the on position, to produce on output leads 16, 16' and 56 voltage signals which are proportional to the instantaneous spherical coordinate target rates 0, E0 and 1.30 respectively. These output voltage signals are respectively supplied together with the error voltages received from the radio automatic or optical manual tracking apparatus as the input signals to the azimuth, elevation and slant range servos to rotate the present position azimuth, elevation, and slant range shafts at proportional rates.

Thus, if it be assumed that the target is flying in a constant direction at a constant speed, and that the target is being correctly tracked at lthe director so that the spherical coordinate present position data and the computed rectangular coordinate rate data fed to the regenerative tracking mechanism are all correct, then the spherical coordinate rate voltagesignals, which the regenerative tracking Imechanism computes and supplies to leads 16, 16' and 56, will be of the proper magnitude in themselves to cause the director to properly track the target thereafter. Thus, once regenerative tracking has been established, no voltage signal need be supplied by the radio or optical tracking mechanism, as long as the target maintains a constant course and speed. Should the target change its course or speed, the voltage signals supplied to thefservos from the regenerative tracking mechanism will no longer be such as to cause the director to properly track the target, and the radio or optical tracking apparatus will then have to supply compensating component voltage signals to the servos in order to rerestablish correct tracking. When correct tracking has thus been established, the regener-ative tracking mechanism will again take over and supply the proper signals to the servos provided the target maintains its new course and speed. Y

In the above discussion it was pointedrout that correct tracking had to be once initially established before the regenerative tracking mechanism could compute the proper voltageA signals to continue the correct tracking. In initially getting on the target, it will be seen that no matter how erroneous are the voltage signals that are initially produced by the regenerative tracking mechanism, the radio automatic or manual optical tracking apparatus can completely override these erroneous signals, and can initially get on the target and establish l-correct tracking by providing error voltage signals which, when added to the erroneous voltage signals from the regenerative tracking mechanism, produce the resultant servo voltage signals which will produce Whatever tracking rates are necessary. Thus, the radio automatic or optical manual tracking system, depending upon the position of switches 4, 5, are always in complete control regardless of the regenerative tracking mechanism.

Accordingly, during the process of getting on the target, the regenerative tracking mechanism and either the radio or optical tracking systems each supply one component of the servo signals. As the tracking process continues, that component supplied by the regenerative mechanism gradu`- ally approaches the correct value and that Vcomponent v supplied by the radio or optical system is gradually reduced,.until finally the former component reaches the correct value and the latter component is zero., A s previ` ously stated, the regenerative tracking mechanism will continue thereafter to automatically maintain correct tracking Without further signals from the radio or optical systems as long as the target maintains a constant course and speed. y

Before describing the regenerative tracking apparatus l l I will first describe the rectilinear converter and rate deriving mechanisms to illustrate how the various terms are derived and supplied to the regenerative tracking apparatus.

All of the apparatus thus far described in general has for its purpose the positioning of shafts 1, 2 and 3 in accordance with the present position of the target in azimuth, elevation and slant range, respectively. This spherical coordinate, present position data is received by the rectilinear converter 25 which transforms the spherical coordinate data into corresponding present position rectangular coordinate data (x0, y and zo), which is produced as proportional angular displacements of output shafts 73, 74 and 75, respectively. As a necessary step in this computation, present horizontal range (R0) is obtained, and this appears as a proportional rotation of output shaft 71.

The rectilinear converter 25, which is shown in FIG. 2, consists essentially of tWo types of computing components, (1) multiplying units vand (2) sine and cosine units, both of which are dead-beat mechanical calculators. The multiplying units are preferably of the type described in U.S. Patent No. 2,194,477, for Multiplying Machines, issued March 26, 1940, in the names of W. L. Maxson and P. J. McLaren. As described in that patent, such a multiplying unit is adapted to produce a rotation of its output shaft instantaneously equal to the product of the rotations of its two input shafts.

The principal element of the above-rnentioned Patent No. 2,194,477 is a spiral gear having teeth mounted thereon in such a path that a follower gear in contact with these teeth is rotated by an amount proportional to the square of the amount of rotation of the spiral gear. The sine and cosine units may consist of two such spiral gears, the path traced out by the teeth of each of which is modified such that in one case the rotation of the driven follower gear is proportional to the sine of the rotation of the spiral gear, and in the other case the rotation of the driven follower gear is proportional to the cosine of the rotation of the spiral gear. The Maxson sine and cosine unit is a well-known device of this character. K

Referring again to FIG. 2, present elevation (E0) data is supplied to the sine and cosine unit 7o from input shaft 2. The sine and cosine unit 76 calculates sin E0 and cos E0, and transmits sin E0 to the multiplying unit 77, as by shaft 7S, and transmits cos E0 to the multiplying unit 79, as by shaft 80. Multiplying unit 77, having also received slant range (D0) from input shaft 3, produces as a proportional rotation of its output shaft 81 the vertical component (zo) of the present ltarget position, which is the product D0 sin E0. Similarly, the horizontal component (R0) of slant range (D0), which is the product of D0 received from shaft 3 and cos En received on shaft 80, is obtained in multiplying unit 79, and is transmitted to a dead-beat torque amplifier d2 by shaft 83. The torque amplifier 82may be of any suitable type adapted to produce as on output shaft 84 a torque amplified signal (R0) which is identical to the input signal (Ra) on shaft 83 but for its greater torque. The wellknown torque amplifying device consisting of contacts, a capacitance motor and a Lanchester damper may, for example, be used for this purpose.

For a more complete understanding of a damper such as the Lanchester damper, reference may be had to the publication of The Society of Naval Architects and Marine Engineers entitled Marine Engineering, volume 11 at pages 105 and 106, andralso to the publication Mechanical Vibrations, by Den Hartog at pages 255 and 256.

The torque amplified horizontal range signal (R0) appearing on shaft 84 is transmitted through gearing to horizontal range output shaft 71. This horizontal range signal is also introduced into multiplying units 85 and S6. Sine and cosine unit 37, having received present azimuth (A0) on input shaft 1, calculates sin A and cos A0, and transmits the former to the multiplying unit 85, as on shaft 8S, and transmits the latter to multiplying unit Se, as on shaft 89. Multiplying unit S5, having received sin A0 from the sine and cosine unit 87 and R0 from Ithe torque amplifier 32, produces as a proportional rotation of its output shaft the East-West coordinate (x0) of the present position of the target, which is the product R9 sin A0. Zero azimuth is taken as the position x, or East direction, and the positive azimuth direction is taken as clockwise. Similarly, multiplying unit S2, having received cos A0 from the sine and cosine unit 37 and R0 from the torque amplifier 82, produces as a proportional rotation of its output shaft 91 the North-South coordinate (y0) of the present position of the target, which is the product R0 cos A0.

There are thus produced on output shafts 90, 91 and 81 of rectilinear converter 25 angular displacements proportional to the x, y, and z components of the present position of the target, referred to the director as the origin of the coordinate system. In order to convert this present position data into corresponding rectangular coordinate data having the guns as the origin of the coordinate system, three parallax knobs 92, 93 and 94 (see FIG. 1) are provided which may be respectively displaced in accordance with the linear distance from the guns to the director in the East-West (x) direction, North-South (y) direction, and Vertical (z) direction, respectively. The displacements of knobs 92, 93 and 94 are additively combined in differentials 95, 96 and 97 with the displacements of shafts 73, 74, and 75, respectively, to thereby produce upon shafts 98, 99, and 100, respectively, angular displacements proportional to the x, y, and z components of the present position of the target, with the origin of the rectangular system taken at the guns.

It will be understood that knobs 92, 93 and 94 have associated therewith a relatively movable dial and index so that the operator may know when he has set in the proper parallax. Such a dial and index will be understood to be associated With all other knobs provided on the director for setting in data.

The present position rectangular coordinate data, now represented as proportional rota-tions of shafts 93, 99 and 100, are introduced into the differentiating, smoothing and predicting circuit 61. Time of flight (tp) data is also introduced into the predicting circuit 61 as a proportional rotation of input shaft 101 but forms no part of the present invention. As previously noted, it is the function of predicting circuit 61 to differentiate the rectangular coordinate input data to thereby obtain the cornponent target rates in rectangular coordinates, Which are produced as angular displacements of output shafts 62, 63 and 64.

ln FIG. 3 there is shown that portion of the differentiating, smoothing, and predicting circuit which operates on the x component. As is there shown, the x0 present position input shaft 93 operates into a differentiating circuit consisting essentially of variable speed drives 102 and 103 and their associated shafts and differentials. Thissmoothing and differentiating circuit operates to produce upon shaft 104 an angular rotation proportional to a smoothed version of the x component of the present position of the target, the unsmoothed version of which is represented by the angular displacement of input shaft 98. Also, the smoothing and differentiating circuit operates to produce upon Shaft 1&5 an angular displacement proportional to a smoothed version of the component target rate (.1110) in the x direction. Shaft 105 is connected to output shaft 62 which shaft is thereby displaced in accordance with the x component of target rate :130.

As above stated, the two Variable speed drives 102 and 103 operate on the x0 signal, received as a proportional rotation of input shaft 98, to produce, as a proportional rotation of shaft 104, a smoothed signal in which the spurious perturbations contained in the x0 input signal 13 have been averaged out, and on shaft 105 a signal corresponding to the smoothed time derivative, or rate of change, of the input x signal. The manner in which this is accomplished will now be described.

The x Acomponent (x0) of the present target position, as indicated by the angular displacement of input shaft 90, is connected into an equating differential 106, the output shaft 107 of which is lpositioned in accordance with the difference between the'angular displacements of input shafts 9S and 104. Shaft 107 positions the ballcarriage 108 of variable speed device 103 through rack and pinion arrangement 109 and other suitable interconnecting gearing. As is well known, ball-carriage 103 transmits the motion of the disc 110, which will, for the present, be assumed to be driven at a constant speed, to the cylinder 111 in such a way that the rate of rotation of cylinder 111 is proportional to the displacement of ball-carriage 10S from the center of disc 110.

The angular displacement of cylinder 111 is connected, as by shaft 112, into a second differential 113, the otherv input of which is supplied from shaft 107 through interconnecting shaft 114. The output of differential 113, which is the algebraic sum of its two inputs, actuates the shaft 115, which in turn displaces the ball-carriage 116 of the second variable speed device 102 through rack and pinion gearing 117. Ball-carriage 116 of variable speed device 102 variably transmits the rotation of the disc 118, which is driven by the constant speed motor 119, to the cylinder 120. The cylinder is gonnected as by shaft 121 to actuate one input member of a differential 122. The other input member of the differential 122 is actuated in accordance with the displacement of cylinderv 111 of variable speed device 103 through shafting 112, 105 and 123. The output member of differential 122, which is thus actuated in accordance with the algebraic sum of the displacements of shafts 121 and 123, is connected to output shaft 124, which in turn actuates the smoothed present position shaft 104, which then supplies the subtractive input to equating differential 106.

In considering the operationV of the smoothing and differentiating circuit, it will first be assumed that the variable speed device 103 and the differential 113 are omitted so that the shaft 115 is directly actuated from shaft 107. The circuit would then constitute' the ordinary differentiating circuitwhich, as is Well-known, would reach a condition of equilibrium when the ball-carriage 116 had assumed such a position that the angular rate of rotation of shaft 104 was equal to the angular rate of rotation of the inputfxo) shaft 98. At equilibrium the angular positionv of shaft 115 Would represent the time derivative (dro) smoothed to a certain extent. Shaft 104 would be actuated in accordance with x0, also smoothed to a certain extent, but it would lag (x0) by an` amount proportional to the displacement of ball-carriage 116 from its central position, so that it could not be employed as a source of smoothed present position data.

By incorporating the additional variable speed device 103 inthe'circuit, the lag is automatically removed from shaft 104 so that its angular position is an accurate, smoothed indication of the (x0) presentposit-ion data. Also a much more effectively smoothed time derivative (dro) is obtained as a proportional rotation of the (no) shaft 105. v

With the variable speed device 103 incorporated in the circuit it will be seen that the circuit can no longer reach equilibrium when the rate of rotation of shaft 104 first equals that of shaft 9S, because at this time shaft 107, and consequently ball-carriage 108 of variable speed device 103, will be displaced an amount proportional to the previously mentioned angular displacement lag of shaft 104 with respect to shaft 98. Therefore,` at this time the cylinder 111 is still rotating, and will Acontinue to act throughdifferential113 to rotate shaft 115 and thereby further displace ball-carriage 116 of variable speed device 102, with the result that the rate of rota- Ation of shaft 104 will begin to exceed that of shaft 93.

tion of shaft 104 is equal to that of shaft 98 and when` there is no angular displacement lag between the two shafts, that is, when shaft 107 and ball-carriage 108 have returned to their zero displacement positions.

Since one condition for equilibrium in the present circuit is that there be no angular displacement lag of shaft 104 with respect to the (x0) input shaft 98, it is apparent that the angular displacement of the (x0) shaft 104 is proportional to a smoothed value of xg.

Also, since the rates of rotation of shafts 104 and 98 are equal at equilibrium, that is, when ball-carriage 116 is stationary, the angular displacement of shaft 115 is proportional to a smoothed version of the time derivative (ai/'0) as in the ordinary differentiating circuit which does not incorporate the variable speed device 103. At equilibrium, however, it was seenthat shaft 107, which provides one input to differential 113, had returned to a position of zero displacement so that the total angular displacement of shaft 115 must have been produced from shaft 112 which is the other input todifferential 113. Therefore, the angular displacement of shafts 112 and 105, and also shaft 62 is also proportional to the smoothed ltime derivative (5&0)

Furthermore, since shaft 112 does not respond to changes in the rate of rotation of input shaft 93, that is, to changes in the time derivative (do), as quickly as does shaft 115, the time derivative (950) which is obtained as a proportional rotation of shaft 105 is more effectively smoothed than theV time derivative which would appear as a proportional rotation of shaft 115 in the ordinary differentiating circuit employing only one variable speed device.

Apparatus similar to that above described is provided, of course, to supply smoothed versions of the time derivatives (go) and (e0).

Referring again to FIG. 3, I have shown a sensitivity control mechanism for varying the proportionality factor of variable speed device 103 or, numerically stated, the ratio of an increment in the angular displacement of shaft 107 to the corresponding increment in the angular velocity of cylinder 111. In the embodiment herein illustrated, a sensitivity control knob 200 is provided, the rotation of which proportionately displaces ball-carriage 201 of a variable speed drive 202 through shaft 203, gearing 204, shaft 205, and rack and pinion gearing 206.

p Diso 207 of variable speed'device 202 is driven from a constant speed motor 208. The cylinder 209 of variable speed device'202 actuates the disc 110 of variable Aspeed device 103, the speed of which determines the circuit constant or proportionality factor of variable speed device 103. Thus, by operationvof sensitivity control knob 20,0, it is possible to vary said proportionality factor as desired. If desired, a spring and detent arrangement could be provided associated with control knob 200 so as to provide an indication sensitive to the operator, of the particular settings of knob 200 Vcorresponding to particular values of said proportionality factor or desiredl sensitivities of the smoothing and differentiating circuit.

If desired a sensitivity control could be provided for each of the x, y, and z prediction circuits. It is contemplated, however, that the same sensitivity control is to be used for all three. It is understood, therefore, that the rotation of the cylinder 209 of variable speed device 202 is employed to actuate not only disc of variable speed device 103, but also the corresponding discs of both the y and z prediction apparatus.

Although in the drawings and in the foregoing description I have disclosed one form of sensitivity control for the differentiating circuit of FIG. 3, I may use a sensitivity control of the character of those illustrated and described in US. lapplication Serial No. 470,686, led on or about December 20, 1942, in the names of D. I. Campbell and W. G. Wing, now IUS. Patent N o. 2,492,355.

One embodiment of suitable regenerative tracking mechanism for solving Equations l to 4, hereinbefore presented, is shown in FIG. 4. As there shown, input shafts 65, 66 and 67, the angular displacements of which lrepresent the rectangular coordinate rates do, y0, zo, respectively, actuate rotor windings 125, 126 and 127 of rotary transformers 123, 129 and 13). Each of these rotary transformers has its stator windings 131, 132 and 133 supplied from a constant source of alternating voltage. The rotor windings are each shown at right angles to their respective stator windings, in which position zero voltage will be induced in these rotor windings. This zero voltage position of the rotor windings corresponds to the zero displacement positions. of shafts 65, 66 and 67. As is well known, as the rotor windings are rotated from their zero signal position, a voltage will be induced therein proportional to the sine of the angle through which they have been rotated. For small angles of rotation from the zero position, the induced voltage will be substantially proportional to the angle itself. The proportionality factor between the angular displacements of shafts 65, 66 and 67 and the component target rates represented thereby is made by design such that the rotor windings are only rotated through small angles for the maximum target rates likely to be encountered. Accordingly, the voltage induced in rotor windings 125, 126 and 127 will be substantially proportional to the rectangular target rates do, 'J0 and a0, respectively.

The induced voltage in rotor winding 125 is applied across one stator winding 134 of a rotary transformer 135. Similarly, the induced voltage in rotor winding 126 is applied across another stator winding 136 of rotary transformer 135. Stator windings 13d and 136 of rotary transformer 135 are in spaced quadrature, that is, the magnetic fluxes produced by these two windings are at right angles with respect to each other. These magnetic uxes are superimposed upon each other in rotary transformer 135 and will each induce a component voltage in rotor windings 137 and 133. Rotor windings 157 and 138, which are also in spaced quadrature, are actuated in accordance with present azimuth (A) from input shaft 63.

The component voltage induced in rotor winding 138 yas a result of the voltage across stator winding 13o will be proportional to the voltage across stator winding 1315 and the sin of the angle through which the rotor winding has been displaced. This component will therefore be equal to the quantity y0 sin A0. The component voltage induced in winding 13S from stator winding 134, will be proportional to the quantity do cos A0 and will be of the opposite phase. Accordingly, the total resultant voltage induced in winding 138 will be proportional to the quan- J'J() COS flo-"lilo Sin AU.

This resultant voltage is placed across the resistive winding 139 of a potentiometer unit 141i, the movable contact arm 141 of which is actuated in accordance with present horizontal range (R0) from input shaft 72. Winding 139 is wound such that the resistance from one terminal to the point of contact with movable arm 141 varies inversely with the angular displacement of the contact arm. Thus, the output voltage existing etween contact arm 1.41 and one terminal of winding 139 will be proportional to the voltage Iapplied to the terminals of winding 139 and inversely proportional to the angular rotation of shaft 7 2. This output voltage, which is applied across the primary winding 142 of transformer 143, will therefore be proportional to the quantity y0 cos Ao-a'zu sin A0 Ro 16 which quantity will be seen to be equal to the desired taret azimuth rate (o) in accordance with Equation 1.

By similar reasoning, it will be apparent that the voltage induced in rotor winding 137 will be proportional to the quantity :to sin A04-'1,70 cos A0, which quantity is equal to R0 in accordance with Equation 4. This voltage, corresponding to horizontal range rate, is introduced into an amplifier 144, and the output is employed to energize one stator winding 14S of a rotary transformer 14o. The other stator winding 147 is positioned in spaced quadrature with respect to winding 145, and is energized in accordance with vertical rate (do) from winding 127 of rotary transformer 1311.

Rotary transformer 166 has two rotor windings 143 and 149 also mounted at right angles with respect to each other and both positioned in accordance with present elevation (E0) from input shaft 69. Accordingly, there will be induced in rotor winding 149 a voltage proportional to the quantity R0 cos Eu-l-zb sin E0, which quantity is equal to target slant range rate (Dc) as shown in Equation 3. This slant range rate voltage signal is employed to energize the primary winding 151B of a transformer 151.

Rotor winding 148 of rotary transformer 146 will have induced therein a voltage proportional to the quantity zo cos Eo-Rg sin E0, and this voltage is placed across the opposite terminals of the resistive winding 152 of potentiometer unit 153. Winding 152 as wound so as to have an inverse relationship of resistance with respect to angular position similarly to winding 139 of potentiometer 140. The movable Contact Iarm 154 of potentiometer unit 153 is angularly displaced in accordance with target slant range (D0) from input shaft 70. Accordingly, there will be produced between contact arm 154 and `one terminal of winding 152 a voltage proportional to the quantity a0 cos EO-R sin E0 D0 which quantity is equal to the target elevation rate (U) as shown in Equation 2. This target elevation rate voltage is employed to energize primary Winding 155 of a transformer 156.

Alternatively, in connection with obtaining a signal proportional -to (A0), Equation 8 shows that :3.30 COS Ao-:IO sin A() D D0 COS E0 Also, Equation 6 shows that 'o cos .A0-3,70 sin A0=0R0- One may therefore consider the output of winding 13S of rotary transformer as proportional `to OR and feed this output into a degenerative feedback amplifier. The output of said amplifier is then employed to excite one static coil of an elevation cosine transformer, which may be similar to transformer 135 but using but one stator and rotor coil and the rotor coil of which is turned by the En shaft 69. The output of the rotor coil will be proportional to cos E0 and this voltage is fed back in a degenerative fashion to :sa-id amplifier to affect or control the gain thereof. Because of the degenerative feedback of this voltage varying as a cosine function of the elevation angle E0, the output of said amplifier will be varied as an inverse function of the cosine of E0. Therefore the output of said amplifier will be equal to RO cos E0 This signal may be amplified and applied across a potentiometer resistance of the character of that shown at 14o, but in this case the slidable contactor of the potentiometer is rotated by a slant range shaft such as shaft 7i). The output of this potentiometer which is taken across the con- "vide a proper `operating, bias Voltage for the tubes.

which according to the above and EquationiS is equal to o. This signal may then be passed through a demodulator as shown in FIG. 4 in connection with potentiometer 140 to supply a unidirectional voltage having a magnitude and polarity sense corresponding to the magnitude and phase sense of the alternating voltage signal derived from the potentiometer. This unidirectional signal voltage corresponds to that derived from rectiier 159.

It will now be seen that voltage signals corresponding to the spherical coordinate target rates (A0, E and D0) have been computed as required. However, these signals are all in the form of alternating voltages corresponding .in magnitude and phase to the quantity represented thereby. In order to transform these alternating voltage signals `into direct voltage signals having a magnitude and polarity corresponding to the quantities represented thereby, any suitable ty`pe of phase-sensitive rectiers 157, 158 and 159 may be employed. These phase-sensitive rectiers essentially comprise two electron tubes connected so as to have their respective platecurrents ow in opposite` directionsithrough a `suitable resistive lo-ad, across the terminals of which the desired direct voltage output is obtained onoutput leads 56, 16 and 16. The opposite terminals of secondary windings 160, 161 and 162 4of transformers 151, 156 and 143 are respectively connected to the grids of the two electron tubes included within the phase-sensitive rectiers 157, 158 and 159.

In order .to provide a bias voltage for the grids of each of these tubes, batteries 163, 164 and 165 are provided, the grounded positive terminals of which are connected to the cathodes of the tubes. Switches 166, 167 and 168 are schematically indicated as being simultaneously operated from the on-ol switch18. In the on position of these switches, a connection is made from a midpoint of each of the windings 160, 161 and 162 through resistors 169, 170 and 171, respectively, to the point on the batteries 163, 164 and 165, respectively, which will prothe o position of these switches, however, the midpoint of windings 160, 161 and 162 .are connected to the negative terminalV of batteries 163, 164 and 165, respectively, to provide a bias voltage for the tubes of a magnitude beyond the cut-off value, to thereby prevent the tubes from operating. i The midpoints of windings 160, 161 and 162 are connected to ground through condensers 172, 173, and 174, respectively. y'

Accordingly, when switch 18 is in its on position, there will be produced in output 1eads56, 16 and 16 unidirectional voltages corresponding to slant range rate, elevation rate, and azimuth rate,.as desired. On the other hand, when switch 18 is in its oil position, zero voltageswill be produced across these leads since the rectiers are then rendered inoperative. The elect of condensers 172, 173 and 174 and resistors 169, 170 and 171 will be to prevent the bias voltage on the grid ofthe tubes from going from its operating value to a value beyond cut-olrimmediately as the switch is changed from an on to an oil position, and vice versa. Thus, as switch 18 is changed from an o to an on position, the direct voltage on output leads 56, 16' and 16 will only gradually build up to their proper values corresponding to the voltages lacross windings 150, 155 and 142 of transformers 151, 156 and 143.

In the previous description of the oper-ation of the regenerative tracking mechanism, it was assumed that the regenerative tracking `unitwa-s `in yoperation during the process of getting on the ,target and establishing proper tracking. Another -mode of operation is -to initiate correct tracking originally wi-th the regenerative tracking mechanism not operating, that is, with switch 13 inthe oli position. In such a case, the auto-maticradi'o or manual optical `tracking systems -alone would be employed to initially establish correct tracking. YWith correct tracking established, the proper angular rate voltages will be produced yacross primary windings 150, 155 and 142, but lthese voltages would be lineiective in producing Yvoltages across output leads 56, 16', and 16, since switch 18 would be in its oil position. NOW when switch 18 is placed in its on position, the proper spherical coordinate rate voltage signals for the servos will build up in leads 56, 16 and 16, but because of the previously explained operation of condensers 172, 1-73 and v174 and resistors 169, 170 and'17'1 these voltages will build up gradually, giving the manual operator or the radio apparatus time lto gradually diminish the rate voltages supplied by them to zero. In this way the regenerative tracking `mechanism can take over without any interruption in the proper tracking of the target.

By employing a regenerative tracking mechanism as described, more accurate tracking is obtained both in radio automatic Iand, in optical manual operation. In optical manual operation, for instance, it will be clear that the -azimuth and elevation operators need only supply that componentof voltage to the azimuth and elevati-on servos to compensate for the amount the rate voltage signals supplied by the regenerative tracking system may be in error. During the times thatthe target is liying at constant speed and course :and the operation of the regenerative tracking mechanism has become fully established, the azimuth yand elevation operators have nothing to do at all. Thus, since their job is made -simplie-r, they can ,accomplish it in =a much more accurate manner.

In radio ,automatic operation the advantages of the regenerative tracking mechanism are even more pronounced. Thus, if we assume that the target is flying al course such that the present position shafts rmust be continuously operated by their respective servos, for example, as a. straight line course, it will be seen that error signals must be continuously supplied to the servos trom the radio sighting system in order to cause the present position shafts to move at all. But the radio sighting system can only supply error voltages when an actual error exists between the line of sight defnedby the radio system and .the actual target orientation. Accordingly, were the radio sighting system alone to be employed for tracking a moving target,

perfect tracking could never be accomplished, since there would always have lto be some error in order to actuate `the servos. Of course, this err-or can be made very small by having :a very high amplification factor in the servos. By employing Vthe regenerative tracking systemin conjunction with the radio sighting system, however, it is possible to completely eliminate these errors during the times that the target is flying la constant course and speed. In such a case, the regenerative tracking system is supplying `all of the voltage required bythe yservos in order properly to track the target, and the radio sighting system is supplying zero error voltages, which means that no errors exist between the line Iof sight deiined by the radio sight-ing system and the actual target orientation.

The regenerative tracking mechanism 1 7 m-ay be employed to `advantage in conjunction with Ian entirely different type of tracking system than that shown in FIG. 1, and previously described. One example of -a modilied type lof tracking system employing regenerative tracking mechanism -17 is illustrated in FIG. 5, wherein only control in elevati-on is shown, the azimuth and slant controls being identical thereto. In FIG. 5 theV regenerative tracking mechanism is shown operating only in conjunction with manual tracking, no provision being made lfor radio automatic tracking.

As shown in FIG. 5, the same regenerative trackingV 'mechanism 17 having the same inputs and outputs as shown in FIG. 4, and previously described, is employed; In this case, however, the servo voltage signals are wholly supplied from the output voltage leads 56, 16 and 16 of the regenerative tracking mechanism. Thus, lead lo* is connected directly to the elevation servo 2. The eleva- .tion servo 26 actuates the present elevation shaft 2 through intermediate s-hafting 175 and differential ll76. The other input member of differential 176 is actuated from shaft E77, which in turn is controlled by the elevation operator :through the elevation handwheel 1?7'8. As before, the se-rvo unit is of the type such that output shaft E75 is driven at a rate proportional to the magnitude of the signal received on lead 16.

it will be seen that present posi-tion shaft 2, which controis the tracking telescope in elevation, has two components of control, one component being provided by the elevation handwheel operator and the other component being provided by the elevation servo as controlled by the regenerative tracking mechanism i7. Thus, regardless of the voltage signals existing at any particular time on lead 1d and the corresponding rate of rotation of shaft 17:7, the actual position of shaft 2 and of the tracking telescope is completely under the control of the operator. The operator therefore displaces his handwheel 78, and the tracking telescope, as required in order initially to establish correct tracking. When correct tracking has been established, the regenerative tracking mechanism 1'7 will cause shaft 175 to rotate at the rate required in order to maintain correct tracking. Thus, the component of control Which the elevation handwheel operator must introduce in order to maintain correct tracking will have been reduced to zero, and thereafter `the elevation handwheel operator will only have to compensate for changes in target course and speed.

Although l have described my invention in coniunction with a tra-cking mechanism to track targets such as aircraft which are movable in azimuth, elevation and range, it is to be understood that my invention is not necessarily limited thereto but may be employed in other fields Wherein controlled angular movements of a member may be continued during intervals of loss of a primary 1control in accordance with pre-established data based on rectilinear coordinate values of the angular movement of the member or a controller or reference.

Hence, While I have described my invention in preferred embodiments and usage, it is to be understood that the words which I have used are Words of description and not of llimitation and that changes within the purview of the appended claims may be made Without departing from the true scope and `spirit of the present invention in its broader aspect.

What is claimed is:

l. In a gun director, an automatic tracking mechanism comprising a radio sighting system, having azimuth, elevation, and range control members determining the position in space dened by said system, rand including means for obtaining azimuth, eleva-tion, and range error signals representing the difference between said defined position and the position of a target, .a computing mechanism responsive to said members for computing signals proportional 4to rate of change of azimuth, elevation, and range, and servo-motive means for driving said members at rates proportional to the respective sums of said error signals and said rate signals.

2. ln .a gun director, a regenerative tracking system comprising a plurality of members, the positions of which represent the spherical coordinates of the present position of the target, la computing mechanism responsive to said members for computing signals proportional to the rate of change ofthe spherical coordinates, and servo-notive means respectively responsive to said rate signals for driving said members at rates proportional to said signals.

3. Apparatus, as claimed in claim 2, further including sighting means lactuated by said members, and independent manual means for `adjusting the position of said meme bers.

4. Apparatus, 'as claimed in claim 2, further including a radio sighting system actuated by said members, and

means responsive to said radio sighting system for correcting said rate signals,

5. Apparatus, as claimed. in claim 2, further including an optical sight actuated by said members, and manual means for correcting the signals proportional to rate of change of the spherical coordinates to maintain the position defined by said sight coincident with the position of a target.

6. ln a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member, means for providing signals proportional to the rate of change of the rectilinear coordinate values of the position of said member, and means for controlling said driving means in accordance with said signals.

7. ln a device of the character described for positioning a member in accordance With the position relative thereto ot an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member, means for providing signals proportional to the angular rate 0f change of the rectilinear coordinate values of the position or said member, means for providing signals proportional to the range of said object, and means for controlling said driving means in accordance with all of said signals.

8. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member, means for controlling the rate of said driving means, means for providing signals proportional to the range of said object, and means for further controlling the rate of said driving means in accordance with said signals and as an inverse function of the range of said object.

9. In a device of the character described for positioning a member in accordance with the position relative thereto of an obiect movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member, means for providing signals proportional to the angular rate of change of position of said member, means for providing signals proportional to the range of 'said object, and means for controlling said driving means m accordance with both of said signals. i l0. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said members, means for driving said member, means for controlling said driving means to position said member in accordance with the position of said object, means for providing signals proportional to the rate of said driving means, means for providing signals proportional to the range of said object, and Jeans for further controlling said driving means in accordance with said signals.

11. Tracking apparatus comprising a rotatably supported device for defining a line of sight to a target, means for driving said device at variable rates, means for measriring the range of said target, a computing means having mputs for receiving a measure of the angular position of said device and the range of said target for providing as an output a measure of the angular rate of said target, and means responsive to said output for controlling the rate of said driving means.

12. Tracking apparatus comprising a rotatably supported device for defining a line of sight of a target, means for driving said device at variable rates, means for controlling the speed of said driving means, means for measuring the range of said target, a computing means having inputs for receiving a measure of the angular position 21 of said device and the range of said target for providing as an output a measure of the angular rate of said target, and means responsive to said output for further controlling the rate of said driving means.

13. Tracking apparatus comprising a device for defining a line of sight to a target, means for supporting said device to rotate in azimuth and in elevation, means for driving said device in azimuth and in elevation at variable rates, means for controlling the speeds of said driving means, means for measuring the range of said target, means for providing a measure of the angular position of said device in azimuth and elevation, means responsive to said angular position and range measures for computing the rate of change of angular position of said device,

and means controlled by said last-mentioned means for further controlling the speeds of said driving means.

14. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member mounted for movement about an axis, means for driving said member about said axis, means for deriving a irst signal for controlling the angular rate at which said driving means operates, computing means for providing as outputs thereof measures of the angular rate of said driving means in rectilinear coordinate values, means for deriving from the output of said computing means a signal proportional to the angular rate of said driving means, and means for controlling said driving means by both of said signals whereby to maintain pre-established driving rates during intervals of zero value of said rst signal.

15. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member mounted for movement about an axis, means for driving said member about said axis, means for deriving a first signal for controlling the angular rate at which said driving means operates, means for resolving the angular Vrate of said driving means into rectilinear coordinate values, means for providing a measure of the range of said object, and means controlled by said two last-mentioned means for providing a second signal, and means for controlling said driving means by both of said signals whereby to maintain pre-established driving rates during intervals of zero value of said rst signal.

16, In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member mounted for movement about two relatively angularly disposed axes, a pair of means for respectively driving said member about said axes, means for deriving signals for controlling the angular rates at which said driving means operate, computing means for providing as outputs thereof measures of the angular rates of said' driving means in rectilinear coordinate values, means for deriving from the output of said computing means signals proportional to the respective angular rates of said driving means, and means for controlling both of said driving means by respective ones of said irst and last-mentioned signals whereby to maintain pre-established driving rates during intervals of zero value of said first-mentioned signals.

17. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member mounted for movement about two relatively angularly disposed axes, a pair of means for respectively driving -said member about said axes, means for deriving signals for controlling the angular rates at which said driving means operate, computing means for providing as outputs thereof measures of the angular rates of said driving means in rectilinear coordinate values, computing means for providing as an output thereof a measure of the range of said object,

. 22 means for deriving from the outputs of both of said computing means signals proportional to the respective angular rates of said driving means, and means for controlling both of said driving means by respective ones of said first and last-mentioned signals whereby to maintain preestablished driving rates intervals of zero value of said tiret-mentioned signals.

18. In a device of the character described for positioning a member in accordance with t-he position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member,v means for controlling the speed of said driving A means, means for supplying a signal proportional to the rate of change of position of said member, means for modifying said signal in accordance with the range of said object, and means responsive to the modified signal for further controlling the rate of said driving means whereby to maintain pre-established driving rates during inoperative periods of said first-mentioned speed control means.

19. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, means for driving said member, means for controlling the speed of said driving means, means for obtaining signals proportional to rectilinear coordinate values of the angular position of said member, means for determining from said signals the rate of change thereof, means for providing signals proportional to the range of said object, and means for further controlling the rate of said driving means as a function of the signals proportional to rectilinear rates and range.

20. A device of the character recited in claim 19 in which the first-mentioned control means for controlling the speed of said driving means comprises manually operable signal supplying means connected in controlling relation to said driving means'.

21. A device of the character recited in claim 19 in which the first-mentioned control means for controlling the speed of said driving means comprises radio wave transmitting and receiving apparatus having a directivity axis and means for providing a signal from said receiving apparatus proportional to the angular disagreement in position of said member and object.

22. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member supporting means for movably supporting said member, means for driving said member, means for controlling the speed of said driving means, means for supplying a signal voltage proportional to the rate of change of position of said member, means for modifying said signal voltage inversely as a function of the range of said object, and means for further controlling said driving means by said signal whereby to maintain pre-established driving rates during inoperative periods of said first-mentioned speed control means.

23. Tracking apparatus comprising a rotatably supported device for dening a line of sight to a target, means for driving said device at variable rates in azimuth and in elevation, means for controlling said driving means, means for providing velocity signals proportional to the output rates 0f said driving means, means for providing signals proportional to the range of said target, means for modifying said velocity signals by said range signals, and means for additionally controlling said driving means in accordance with the modified velocity signals whereby to maintain pre-established driving rates during inoperative periods of said first-mentioned control means.

24. Tracking apparatus comprising a rotatably supat variable rates in azimuth and elevation, means for controlling said servo-motors, va range servo-motor and control means therefor including radio Wave responsive means for causing said servo-motor to `provide an angular output as a measure of the range of said target, means for providing measures of the output rates of said azimuth and elevation servo-motors, computing means having as inputs said rate and range measures and being operable to modify said rate measures by said range measure to provide outputs respectively proportional to `the angular rates of said azimuth, elevation and range servo-motors, and means for respectively and additionally controlling said servo-motors by the outputs of said computing means whereby to maintain pre-established driving rates during inoperative periods of said irstmentioned control means.

25. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting said member, servomotor means for driving said member, means for controlling said servomotor. means to position said member in accordance with the position of said object, means for deriving a signal dependent upon the rate of change of position and the rate of change of range of said object, and means for further controlling said servomotor means by said last mentioned signal.

26. In a device of the character described for positioning a member in accordance with the position relative thereto of an object movable in angular relation thereto and in range therefrom, a member, supporting means for movably supporting .said member, and servomotor means vsignals proportional to the spherical coordinates of saidA target position, means for converting the signals proportional to spherical coordinate measures to signals proportional to rectilinear coordinate measures of target position, and means `for actuating said sighting means in accordance with `the signals proportional to the rectilinear coordinates of target position.

References Cited by the Examiner UNITED STATES PATENTS 1,936,442 11/33 Willard 33-49.3 2,004,067 6/35 Watson 23S-61.5 2,340,865 2/44 Chafee 23S-61.5 2,399,726 5/46 Doyle 33-493 2,409,448 10/46 Rost 343--7 2,414,108 1/47 Knowles et al. 343--117 X 2,416,562 2/47 Alexandersen 343-7 2,438,112 3/48 Darlington.

'KATHLEEN H. CLAFFY, Primary Examiner.

CHESTER L. JUSTUS, NORMAN H. EVANS, JAMES L. BREWRINK, R. G. NILSON, S. YAFFEE,

Examiners. 

1. IN A GUN DIRECTOR, AN AUTOMATIC TRACKING MECHANISM COMPRISING A RADIO SIGHTING SYSTEM, HAVING AZIMUTH, ELEVATION, AND RANGE CONTROL MEMBERS DETERMINING THE POSITION IN SPACE DEFINED BY SAID SYSTEM, AND INCLUDING MEANS FOR OBTAINING AZIMUTH, ELEVATION, AND RANGE ERROR SIGNALS REPRESENTING THE DIFFERENCE BETWEEN SAID DEFINED POSITION AND THE POSITION OF A TARGET, COMPUTING MECHANISM RESPONSIVE TO SAID MEMBERS FOR COMPOUNDING SIGNALS PROPORTIONAL TO RATE OF CHANGE OF AZIMUTH, ELEVATION, AND RANGE, AND SERVO-MOTIVE MEANS FOR DRIVING SAID MEMBERS AT RATES 